A well documented and inherent difficulty in the parallel transmission of analog/digital information over a transmission medium, such as a plurality of parallel transmission lines, is signal crosstalk resulting from capacitive and inductive coupling within the transmission medium. The error rate due to crosstalk signal degradation typically increases with increasing speed of data transmission. This is because higher transmission speeds involve a greater number of possible values which make it increasingly difficult to distinguish between signals in the presence of an electrical impairment. The open literature contains a vast number of references which in general attempt to address the problem of signal noise on transmission lines, and in particular, to minimize crosstalk between information transmitted in parallel through a transmission medium having defined characteristics.
One interesting approach is discussed by T. H. Nguyen and T. R. Scott in an IBM Technical Disclosure Bulletin entitled "Propagation Over Multiple Parallel Transmission Lines Via Modes,+ Vol. 32, No. 11, April, 1990. As discussed therein, it is known that electromagnetic waves propagating over two conductors and a ground line have two orthogonal modes referred to as the "even mode" and the "odd mode." In general, n conductors and a ground line have n such orthogonal modes. Because of its orthogonal properties, each mode propagates independent of all other modes. The resolution of line voltages into orthogonal modes is analogous to the concept of resolving a pulse waveform into its orthogonal Fourier components. Just as the Fourier components can be studied separately because they are orthogonal, and hence independent of each other, so the intrinsic orthogonal modes of a plurality of transmission lines can be studied separately since they are also independent of each other.
The above-referenced IBM Technical Disclosure Bulletin describes the simplicity of orthogonal mode determination for those transmission lines having 2, 4, 8, . . . , 2.sup.n conductors symmetrically arranged on a cylindrical surface with respect to a coaxial ground conductor. The calculation of orthogonal modes for certain such transmission line configurations is presented. Although the mathematical groundwork for transmission of intrinsic orthogonal modes over a plurality of parallel transmission lines is discussed in this Technical Disclosure Bulletin, a practical implementation of the concept is lacking. The difficultly encountered is that the propagation of binary signals (for example) via modes is often not possible with only digital (i.e., on/off) signals since the number of modes is equal to the number of conductors (which can be doubled by using plus/minus designations), but the number of binary combinations is exponential, i.e., two raised to the number of conductors n. Therefore, a need exists in the art for a practical approach (such as described herein) to allow the encoding of, for example, each possible binary signal combination as a unique orthogonal mode signal for transmission through a transmission medium having defined characteristics.